#admin{
    width: 80%;
    margin: 0 auto;
}
h3 {
    text-align: left;
    margin: 0 auto;
    /*为了垂直居中*/
    position: absolute;
    top: 8%;
    left: 50%;
    transform:translate(-50%,-50%);
    display: inline-block;
}

.nav-left{
    margin: 100px 0px;
}

.exitadmin{
    float: right;
    cursor: pointer;
    margin-right: 20%;
    display: inline-block;
}